Why are Social Security and Medicare taxes taken out but no federal income tax?
Social Security and Medicare taxes (often labeled FICA, or shown as separate "SS" and "Med" lines) are withheld as a flat percentage of wages starting from the first dollar, with no adjustment for your filing status or W-4 entries. Federal income tax withholding, by contrast, is a graduated calculation that builds in the standard deduction and your W-4 choices, as the IRS explains on its tax withholding for employees page — so it can legitimately come out to zero on a paycheck where FICA is still taken. Seeing FICA but no federal income tax usually means your pay or W-4 settings put your projected income tax at zero, not that payroll made a mistake.
Two taxes, two completely different formulas
It helps to stop thinking of "federal taxes" as one thing. A paycheck carries at least two distinct federal levies:
- Social Security and Medicare tax fund those specific programs. Each is a fixed percentage of your wages, applied uniformly — there's no standard deduction, no brackets at the low end, and no W-4 input. If you earn wages as an employee, these come out, period.
- Federal income tax withholding is a prepayment toward the income tax you'll settle on your annual return. It's computed per paycheck from IRS tables that annualize your wages and account for filing status, dependents, and other W-4 entries, under the rules detailed in IRS Publication 505.
Because the income tax tables build in the standard deduction, a modest paycheck can project an annual income on which no income tax would be owed — so the tables call for zero withholding. The flat FICA percentages have no such floor. Result: FICA lines show amounts, the federal income tax line shows zero, and both are computed exactly as designed.
Common situations where this pattern appears
- Part-time or low-wage work. Each paycheck projects to an annual income within the standard deduction's shelter, so income tax withholding is zero while FICA still applies.
- W-4 credits and deductions. Dependent credits in Step 3 or deductions in Step 4(b) can zero out income tax withholding — but they never touch FICA, because FICA ignores the W-4 entirely. Our guide to how the W-4's sections work shows which lines affect what.
- Claiming exempt. A W-4 marked "Exempt" stops federal income tax withholding only; Social Security and Medicare continue. Publication 505 spells out the conditions for that claim.
- Multiple small jobs. Each employer's payroll sees only its own wages, so each may withhold zero income tax even when your combined income is taxable — while every job withholds FICA from dollar one.
How this shows up on your W-2
At year end the split is visible on the form itself: federal income tax withheld lands in Box 2, while Social Security and Medicare taxes appear in Boxes 4 and 6, per the General Instructions for Forms W-2 and W-3. A W-2 with amounts in Boxes 4 and 6 but $0 in Box 2 is the year-long footprint of exactly this paycheck pattern — our page on reading your W-2 maps every box.
Does it mean you'll owe?
Not necessarily — but it's worth checking rather than assuming. Zero income tax withholding is fine if your actual tax for the year is zero; it's a problem if combined jobs, other income, or a mid-year raise push you into owing. FICA amounts, on the other hand, aren't something you reconcile on an ordinary return — they're not a prepayment of income tax and don't offset what you owe. The IRS Tax Withholding Estimator compares your projected income tax against your actual withholding, and if it shows a gap, the fix runs through a new W-4 — a process we describe in how withholding from a paycheck works.